What is the ideal ergonomic design for your work situation? The following questions will help you decide.

How will the computer be used?
If only one person will be using the computer then the arrangement can be optimized for that person’s size and shape. An adjustable height chair, for instance, may be unnecessary. If several people must use the computer, you’ll need to create an arrangement that most closely satisfies the needs of the extremes – the smallest and tallest, thinnest and broadest persons. Also think about how long people will be using the computer. A few minutes won’t make ergonomic issues a high priority. More than one hour each day, though, may require an ergonomic arrangement.

What kind of computer will be used?
Ergonomic guidelines assume that you’ll be using a desktop system with the computer screen separated from the keyboard. Guidelines for laptop use are more difficult because laptop design inherently is problematic – when the screen is at a comfortable height and distance, the keyboard isn’t and vice versa. For sustained use you should consider purchasing either an external monitor or an external keyboard and a docking station.

What kind of work will the computer be used for?
Try to anticipate the software and activity to be used most often.

Word processing – arranging the best keyboard/mouse position is high priority
Browsing the Internet/graphic design – arranging the best mouse position is high priority
Data entry – arranging the best numeric keypad/keyboard is high priority
Games – arranging the best keyboard/mouse/game pad is high priority

Where should the computer monitor be placed?
The monitor should be:

Directly in front of the user and facing the user, not angled to the left or right, to avoid neck twisting. Also encourage him to use the screen scroll bars to ensure that what is being viewed most is in the center of the monitor rather than at the top or bottom.
At a height that doesn't make the user tilt his head up or bend his neck down to see it. When seated comfortably, a user should look at a point on the screen two to three inches below the top of the monitor. If the monitor is too low, the user will crane his neck forwards. If it's too high he'll tilt his head backwards and end up with neck/shoulder pain.
At a comfortable horizontal distance for viewing, which is approximately an arm’s length (when you sit back in your chair and raise your arm, your fingers should touch the screen). At this distance you shouldn’t need to move your head to see the viewing area of the monitor. If text looks too small, use a larger font or magnify the screen image in the software. Don’t sit closer to the monitor.
In some instances and for some users, such as those who wear bifocal corrective glasses, tilted backwards and the height adjusted for comfortable screen viewing.

Where will the computer be used?
Think about the following environmental conditions.

Lighting. Bright light glare should never be noticeable on the computer screen. If it is, move the screen, lower the light level and get a good-quality, glass anti-glare screen. Also make sure that the computer monitor screen isn't backed to a bright window or facing a bright window (use a shade or drapes to control window brightness).

Ventilation. Ideally, you should have adequate fresh-air ventilation and adequate heating or cooling so you feel comfortable while you're working.

Noise. Noise can cause stress, which tenses your muscles and increases injury risks. Try choosing a quiet place for your workstation, and use low-volume music, preferably light classical, to mask the hum of any fans or other sound sources.

What furniture will you use?
Make sure the computer and its peripherals are placed on a stable working surface with adequate room for proper arrangement. If this work surface will also be used for writing on paper, choose one that’s between 28 and 30 inches above the floor. You should consider attaching a keyboard/mouse-tray system to your work surface. Choose a height-adjustable system that allows you to tilt the keyboard away from you slightly for better wrist posture (negative tilt). When using the mouse, keep your upper arms relaxed and as close to the body as possible.

What chair will be used?
If only one person is using the workstation, the chair can be at a fixed height. But it should be comfortable to sit on and have a good backrest. If more than one person will be using the computer, consider buying a chair with ergonomic features.

Why is posture important?
Good posture is the basis of good workstation ergonomics and the best way to avoid a computer-related injury.

The user should be able to reach the keyboard keys with his wrists as flat (not bent up or down) and straight (not bent left or right) as possible
The user's elbow angle (the angle between the inner surface of the upper arm and the forearm) should be at or greater than 90 degrees, which will help avoid nerve compression at the elbow
The upper arm and elbow must be as close to the body and as relaxed as possible for mouse use. Avoid overreaching. Also make sure that the wrist is as straight as possible when the mouse is being used.
The user must sit back in the chair and have good back support. Also check that the feet can be placed flat on the floor or on a footrest.
Place frequently used items closer to the user so they can be reached comfortably
The user’s body should be centered on the alphanumeric keyboard. Most modern keyboards are asymmetrical in design (the alphanumeric keyboard is to the left and a numeric keypad to the right). If the outer edges of the keyboard are used to center the keyboard and monitor, the user’s hands will be deviated because the alphanumeric keys will be to the left of the user's midline.
Ensure that the head and neck are as straight as possible

Are work breaks important?
All ergonomists agree that it's a good idea to take frequent, brief rest breaks. Practice the following:

Eye breaks. Looking at a computer screen changes how the eyes work, causes you to blink less often and exposes more of the eye surface to the air. Every 15 minutes you should briefly look away from the screen for a minute or two to a more distant scene, preferably something more than 20 feet away. This lets the muscles inside the eye relax. Also, blink your eyes rapidly for a few seconds. This refreshes the tear film and clears dust from the eye surface.

Micro-breaks. Most typing is done in bursts rather than continuously. Between these bursts of activity you should rest your hands in a relaxed, flat, straight position.

Rest breaks. Every 30 to 60 minutes you should take a brief rest break. Stand up, move around and do something else. Go and get a drink of water, soda, tea, coffee or whatever. You’ll exercise different muscles and feel less tired.

Exercise breaks. There are many stretching and gentle exercises that you can do to help relieve muscle fatigue. You should do these every one to two hours. Here are some examples.

Ergonomic software. Working at a computer can be hypnotic, and often you don't realize how long you've been working and how much you've been typing and mousing. You can get excellent ergonomic software to install on your computer. The best software runs in the background and monitors how long you've been using the computer. It will prompt you to take a rest break at appropriate intervals and will suggest simple exercises.

About Professor Alan Hedge, PhD, MErgS, AFBPsS
Alan Hedge is a full professor in the Department of Design and Environmental Analysis, Cornell University, where, since 1987, he has directed the human factors and ergonomics teaching and research programs. Prior to that, for over 10 years he ran the graduate program in applied psychology and ergonomics at Aston University, Birmingham, UK. From 1990 to 1993 he was also an Honorary Research Fellow at the Institute of Occupational Health, University of Birmingham, UK.

His research and teaching activities have focused on issues of design and workplace ergonomics as these affect the health, comfort and productivity of workers. He is currently conducting research on carpal tunnel syndrome risk factors for workers, alternative keyboard system designs, the performance and health effects of postural strain, and on the health and comfort impacts of environmental stressors, such as the effects of indoor air quality on sick building syndrome complaints among office workers, and the effects of office lighting on eyestrain problems among computer workers. He has published a book, 18 chapters and over 130 articles on these topics in ergonomics and related journals.

For more information, visit Cornell University Ergonomics Web site.
Photos courtesy of Herman Miller - www.hermanmiller.com and
SMED International - www.smednet.com.

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